Anyway, apologies for the derail - maybe we should resurrect the Battle of France thread and put that stuff in there.
Per the OP, here is my list:
Douglas SBD Dauntless
Sunk more enemy ships in the critical period of the war than any other type, and pressed into service as a fighter, even shot down a respectable number of enemy aircraft, such that it was critical to the defeat of the Japanese and the salvation of the United States. With the grotesque failure of the American torpedo program, the SBD dive bomber was the main ship killer in the American arsenal. The B-17 was supposed to do the job but early war-planners, including some pretty smart ones, failed to realize how hard it was to hit ships with bombs dropped from 20,000 feet (or even 10,000 feet). Turns out they can see the bombers and turn away. The SBD was maneuverable, carried a respectable bomb load, was rugged and well armed enough to survive sorties at a pretty good rate (much better than the TBD or TBF I believe)
I think the SBD is underrated because it's often portrayed as an obsolete plane (name a better dive bomber deployed in any numbers in 1942?) and generally as an underdog in most literature I've read. And yet, if you sent a squadron of these against an enemy fleet, you could expect enemy ships sunk that day and most of them to come back. This is not something you could say about the Fairey Barracuda or the Blackburn Skua, or even the Helldiver for that matter. The Aichi D3A does come close to this, it certainly sunk a lot of American ships, but it's vulnerability was just a little to high to make my list.
Ki-43 Oscar
The Zero gets the glory, at least to some extent (though also a certain amount of sneering again these days) but according to the Japanese themselves, it was actually the Ki-43 "Hayabusa" that shot down the most allied planes. The Ki-43 may not have achieved 400 mph speeds, was lightly armed, a lack of pilot armor and unprotected fuel systems left them vulnerable to damage particularly in the early models, but the phenomenal maneuverability of the plane put it almost in a class of it's own. It was a major part of the "shock and awe" of early Japanese victories throughout the Pacific and Asia. To me it's a beautiful and deadly aircraft that does not get the respect it deserves.
I think the Ki-43 is underrated because it's typically depicted as flimsy and the Zeros poor cousin, so to speak.
A6M2-N
While it's significance in the war was somewhat limited - this was really the only true float plane fighter ever deployed in any numbers during the war. The closest match would probably be the
Curtiss SC Seahawk, also an excellent plane (and probably at least partly inspired by the A6M2-N) but it came too late to make much of a difference. The Nakajima A6M2-N performed remarkably well in spite of the weight and drag of the floats, and it extended the already extraordinary range of the A6M series of fighters by being deployable to very remote bases that lacked airfields. I don't think the Japanese fully exploited the potential of this aircraft so it's impact on the war was limited, but as a design it was remarkable. Nobody else was able to accomplish this design feat within the still contested periods of the war.
I think the A6M2-N is underrated because almost nobody even knows about it, and it tends to be considered an inferior one-off to the Zero.
P-40
The P-40 was the most important land based fighter in the Anglo-American arsenal in numerous Theaters in 1942 and well into 1943, and played a small but crucial role for the Soviets in the same period, particularly in the defense of Leningrad and Moscow. Though it did have a major flaw in the performance ceiling imposed by the engine, and was disliked by the War Department, plans to phase out the P-40 kept having to be put on hold as it's ostensible replacements and rivals such as the Hurricane, P-39, and P-38 failed to live up to expectations or proved unable to do the job. Heavily armed, maneuverable, and capable of escaping (or catching) enemies in very high speed dives, the P-40 gave Allied pilots a chance where other types failed. The P-40 took control over the skies over China, Burma and India, it held the line at Darwin and Milne Bay (Australias "Battle of Britain"), faced the wrath of the Luftwaffe in North Africa and ended the lives of several of their top Aces. P-40 pilots themselves had a hue number of Aces, over 200 by my last count.
I think the P-40 is underrated because while it is popular with neophytes largely due to its looks and therefore gets some grudging respect, the 'experten' of the aviation history community tend to almost universally deride it. For decades, every book on aviation history reported that the P-40 was unmaneuverable, slow, and obsolete before the war began and totally outclassed by the Zero and the Bf 109. None of these things were true. We now know that the P-40 was one of the most maneuverable (fastest rolling and tightest turning) Allied monoplane fighters, probably second only to the Spitfire, and we know that P-40s shot down more enemy fighters than any other land based type in the Pacific in 1942, and probably in the Med as well. We now know that American, Australian, New Zealand, and Russian aces praised it and considered it more than equal to the A6M and the Bf 109. But the revision lags, and most websites still repeat the same "rugged but obsolete / unmaneuverable" Trope from the 1960s.
Yak-1, 1B, 7, 7B
The Yak series was one of the great fighters of WW2. Its performance was limited to low altitude and build quality was often poor especially in the most crucial war year of 1942. But as a design, this plane was one of the greats. It was fast, well streamlined, made largely of wood so cheap to manufacture, reasonably well armed (nose cannon plus a couple of MGs was sufficient for the excellent Bf 109F series so yeah, I think it's good armament) and extremely agile. By the end of 1942 as the manufacturing problems caused by evacuating most of the factories across the Urals were being worked out, this aircraft became an increasingly deadly menace to the Luftwaffe and probably bore the brunt of destroying German aircraft in that crucial tipping point of the war just after Stalingrad.
I think the Yak series, up to the 9 and the 3, are underrated because they are Russian, and people in the English speaking world and the "West" tend to dismiss their victory claims and all things Russian in general, unfairly I believe. Only the Yak 3 really gets respect because that was the plane the Germans said scared them. The Yak was a design tailored to the Theater and the circumstances, it was a low altitude fighter, it's main job was to shoot down Bf 109s and protect the Sturmoviks and Pe-2s, so it was armed appropriately. But it did the job and it's a beautiful looking aircraft to boot.
Pe-2
I've explained why I like this plane so much. Fast, accurate, versatile. yes it had some limitations and the death of the main designer in an accident probably helped prevent it from being further developed, but it was a very advanced design initially and did the damage the Soviets needed to do to the German war machine in the critical years of the war.
I think the Pe-2 is underrated again, because Russian. And because it didn't carry ten tons of bombs, but neither did the Stuka and look how important that was to the German war machine. Like the Stuka, the Pe-2 was a precision dive bomber, but unlike the Stuka it was fast and well armed with heavy defensive guns. It is also a beautiful aircraft. It deserves more respect than it gets.
A-20
Fastest Anglo-American bomber until the Mosquito. This aircraft was agile, versatile and did the job really well. What took it from a good to a great design in my eyes was its use as a strafer and skip-bomber in the Pacific (and to some extent also in the Med) and it's wide adaptation by many Allies (English, Australians and Soviets) to a wide variety of tasks, especially in the Maritime Theaters, such as where the Soviets used it as a torpedo bomber, and also as a night-fighter and intruder.
I think the A-20 is underrated in the English-speaking world because we put too much emphasis on the four engined heavy bombers and on heavy bomb loads vs. precision and versatility. The A-20 didn't carry 10,000 lb bombs or fly at 35,000 feet, but it probably did more actual harm to the Axis War Machines than those aircraft which did.
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